One type of moving storage data storage device is the disc drive, which has a data storage medium that is fixed in rotation with a motor. The storage medium is thus moved in a data transferring relationship with respect to a transducer. Because of demands for ever-faster access requirements, the speed at which the motor presents a desired sector of the disc to the transducer has evolved to extremely high speeds in relation to what was typical just a few years ago. Also because of demands for ever-greater storage capacity by disc drives of ever-smaller size, the density with which the data is stored to the storage medium has likewise increased exponentially. This increased storage density has made the disc drive designer pay more attention to the source of perturbations that interfere with the desired physical spacing between the storage medium and the transducer during the data transfer activities.
A compressive disc clamp has become a popular solution for fixing the storage medium in rotation with the motor. Generally, this type of clamp has one or more passages for fasteners to pass through and engage the motor. Advancing the fasteners compressingly engages the clamp against the storage medium.
It is very important that the clamp be aligned in rotation with the motor. Otherwise, a non-aligned condition creates unbalanced rotating mass, creating forces that can result in repeatable runout of the storage medium. This can cause fatal data transfer errors between the transducer and the storage medium.
Previous solutions that aligned a surface of a centrally-disposed opening in the clamp with an alignment feature of the motor are no longer feasible as the disc drive size is reduced. The centrally-disposed opening in the clamp is typically already present, as it is used for the fastener. However, it has been observed that as the inner diameter alignment surface is reduced, the error is magnified; that is, slight deflections that were negligible in the past now create out of tolerance conditions. Also, alignment features in the hub near the axis of rotation requires reducing wall thicknesses of the motor hub wall in ways that have been observed to diminish structural integrity beyond what is reliable.
What is needed is a way to align the clamp in relation to an outermost surface of the motor hub, thereby as far away as possible from the axis of rotation. What is also needed is a way of making the clamp self-aligning to the motor as the fastener(s) attach the clamp to the motor. It is to these improvements that the embodiments of the present invention are directed.